// Import types
import MMDDYY from '../../../shared/types/MMDDYY';

// Import shared helpers
import getTimeInfoInET from '../../../shared/helpers/getTimeInfoInET';


/*------------------------------------------------------------------------*/
/* ------------------------------ Constants ----------------------------- */
/*------------------------------------------------------------------------*/

// Number of milliseconds in a day
const DAY_IN_MS = 24 * 60 * 60 * 1000;

// Number of milliseconds in a week
const WEEK_IN_MS = 7 * DAY_IN_MS;

// Ordinals to attach to end of number
const ORDINALS = ['th', 'st', 'nd', 'rd'];


/*------------------------------------------------------------------------*/
/* ------------------------------- Helpers ------------------------------ */
/*------------------------------------------------------------------------*/

/**
 * Get a number's ordinal
 * @author Gabe Abrams
 * @param num the number being analyzed
 * @returns ordinal
 */
const getOrdinal = (num: number): string => {
  return (ORDINALS[(num - 20) % 10] ?? ORDINALS[num] ?? ORDINALS[0]);
};

/*------------------------------------------------------------------------*/
/* -------------------------------- Main -------------------------------- */
/*------------------------------------------------------------------------*/

// FIXME:
/**
 * Extract a description of a date, relative to the current week-day.
 * @author Benedikt Arnarsson
 * @param date the date that info is being displayed for.
 * @returns a string describing the day, relative to the current day.
 */
const dateToDescription = (date: MMDDYY): string => {
  const startOfDay = new Date(date.year, date.month - 1, date.day);

  // Could use dce-reactkit `getMonthName` here
  const month = startOfDay.toLocaleDateString(
    'en-US',
    { month: 'short' },
  );
  const monthAndDate = `${month} ${date.day}${getOrdinal(date.day)}`;

  const dayOfWeek = startOfDay.toLocaleDateString(
    'en-US',
    { weekday: 'long' },
  );

  const currDate = getTimeInfoInET();
  const startOfCurrDay = new Date(currDate.year, currDate.month - 1, currDate.day);

  const msFromStartOfWeek = DAY_IN_MS * startOfCurrDay.getDay();

  // Case 1: within the current week
  const startOfWeek = new Date(startOfCurrDay.valueOf() - msFromStartOfWeek);
  if (startOfWeek <= startOfDay) {
    return `${dayOfWeek} (${monthAndDate})`;
  }

  // Case 2: within the last week
  const startOfLastWeek = new Date(startOfWeek.valueOf() - WEEK_IN_MS);
  if (startOfLastWeek <= startOfDay) {
    return `Last ${dayOfWeek} (${monthAndDate})`;
  }

  // TODO: is there another case? perhaps over a year ago?
  // Case 3: just display the month and date
  return monthAndDate;
};

export default dateToDescription;